TY - JOUR
T1 - Changes in phases and crystallinity of plasma‐sprayed hydroxyapatite coatings under heat treatment
T2 - A quantitative study
AU - Wang, B. C.
AU - Chang, E.
AU - Lee, T. M.
AU - Yang, C. Y.
PY - 1995/12
Y1 - 1995/12
N2 - With three kinds of plasma‐sprayed hydroxyapatite coatings (HACs) prepared, the objectives of this study were (1) to establish the calibration methods for quantitatively measuring the concentration of impurity phases and the degree of crystallinity of the HACs, and (2) to explore the effects of postheat treatments at various temperatures in vacuo on the changes of phases and crystallinity of the HACs. By the internal standard method used, the concentrations of impurity phases, such as α‐TCP, β‐TCP, and TP, of the assprayed HACs were significantly higher than those measured by the direct intensity‐ratio method, and the CaO phase was lower than the direct intensity‐ratio method. When the HACs were heat treated in the temperature interval 630–850°C, the concentrations of impurity phases obviously decreased, and the coating crystallinity apparently increased. After annealing at 850°C, an HAC consisting of at least 95% crystallinity with few impurity phases was obtained. As the annealing temperatures in the interval 850–1000°C were applied, however, the HA phase seriously decomposed, resulting in the appearance of a large number (higher than 20 wt%) of impurity phases in the HACs. This work suggests that the optimum heat treatment conditions in vacuo for maximizing crystallinity and minimizing impurity phases of the HACs do not occur at the same temperature. © 1995 John Wiley & Sons, Inc.
AB - With three kinds of plasma‐sprayed hydroxyapatite coatings (HACs) prepared, the objectives of this study were (1) to establish the calibration methods for quantitatively measuring the concentration of impurity phases and the degree of crystallinity of the HACs, and (2) to explore the effects of postheat treatments at various temperatures in vacuo on the changes of phases and crystallinity of the HACs. By the internal standard method used, the concentrations of impurity phases, such as α‐TCP, β‐TCP, and TP, of the assprayed HACs were significantly higher than those measured by the direct intensity‐ratio method, and the CaO phase was lower than the direct intensity‐ratio method. When the HACs were heat treated in the temperature interval 630–850°C, the concentrations of impurity phases obviously decreased, and the coating crystallinity apparently increased. After annealing at 850°C, an HAC consisting of at least 95% crystallinity with few impurity phases was obtained. As the annealing temperatures in the interval 850–1000°C were applied, however, the HA phase seriously decomposed, resulting in the appearance of a large number (higher than 20 wt%) of impurity phases in the HACs. This work suggests that the optimum heat treatment conditions in vacuo for maximizing crystallinity and minimizing impurity phases of the HACs do not occur at the same temperature. © 1995 John Wiley & Sons, Inc.
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U2 - 10.1002/jbm.820291204
DO - 10.1002/jbm.820291204
M3 - Article
C2 - 8600138
AN - SCOPUS:0029411920
VL - 29
SP - 1483
EP - 1492
JO - Journal of Biomedical Materials Research
JF - Journal of Biomedical Materials Research
SN - 1552-4973
IS - 12
ER -